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Indicator Circuits
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Last Updated on:
Monday, October 03, 2011 06:08 PM
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| Circuits designed
by Dave Johnson, P.E. : |
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DC Current Indicator #4 - The circuit below uses some common components to turn
on an LED whenever DC current above a certain level is detected. The circuit
uses a very popular LM393 dual voltage comparator from National Semiconductor and a
common 1N4148 signal diode. The diode acts as a crude 0.7v voltage reference.
Only one of the comparators inside the 8 pin package is used. A pair of
resistors across the diode forms a voltage divider, which produce a reference
voltage of about 0.015v....
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- DC Current Indicator
6
The circuit below is a simple way to indicate when DC current is flowing through
a wire. The circuit is designed so it will turn on a LED indicator light,
whenever the voltage drop across a shunt resistor exceeds about 0.1 volts. The
value of the resistor can be selected based on the desired current flow. Although I
show a circuit for 12v operation, the circuit can be used over a wide range from 3v
to perhaps 24v....
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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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Car indicator alarm - Schematic only, no circuit description
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Cellular Phone calling Detector - Flashes a LED when detecting
an incoming call. Powered by one 1.5V cell (added 4/05)
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Charge indicator gauges lead-acid batteries - 05/27/99 EDN-Design
Ideas.....Although rechargeable, sealed lead-acid cells are uncommon in
portable applications, they are a good choice for standby
applications, such as emergency lighting and burglar alarms. A key
advantage…PDF has several circuits, please scroll to find this one….
[Design Idea by Fran Hoffart, Linear Technology Corp, Milpitas, CA] |
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Circuit Detects Current Pulses - 01/06/94 EDN-Design
Ideas.....The pulse detector provides a visible indication of positive and
negative current pulses. The pulses amplitudes can vary from20 to150 mA.
The pulses durations can range from10 to40 msec, and their repetition rate
can span40 to180 pulses/minute..... [Design Idea by Richard McGillivray,
Grey Bruce Regional Health Centre, Owen Sound, Ontario, Canada] |
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Circuit forms low-frequency circulator - 11-Oct-01 Issue of EDN The
electronic circulator made its debut ten years ago (Reference 1]. It functioned at VHF
as a three-port unit using a Comlinear (now part of National Semiconductor,
www.nsc.com] CLC 406 operational amplifier. The circuit in Figure 1 extends the
circulator's performance to four-port operation at low frequencies, using the readily
available 941 (equivalent to the ubiquitous 741] and LM3..... [Design Idea by Richard
Kurzrok, Queens Village, NY] |
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Circuit Forms Peak/Clipping Indicator - 11/22/01 EDN-Design Ideas.....The
simple peak detector in Figure 1 is the result of a need for a single-5V-supply,
level/clipping indicator for a multimedia-PC sound system. The design is unique in
that it detects both stereo channels on a single peak-hold capacitor. All the
adjustments in the circuit simultaneously apply to both left and right stereo
inputs..... EDN is migrating links. This link is not verified. Search the
"title" EDN for new link. |
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Circuit indicates ac-mains-fuse failure - 8-Jan-09 Issue of EDN Use
this circuit to alert you when a fuse fails..... [Design Idea by Vladimir Oleynik,
Moscow, Russia] |
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Contactless Mains Voltage Indicator - (circuit / schematic design added
11/06) |
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Cut Phone Line Detector - A while ago I got an email asking for the
schematic of a circuit to detect cut phone lines. It didn't take me long to find this
circuit in Electronics Now. When the circuit detects that a phone line has been cut,
it activates a MOSFET which can be used to drive a relay, motor, etc. It can also be
connected to a security system.... [Arron Cake] |
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Cut Phone Line Detector - This circuit speaks for itself. When the
phone line is okay, Q1 acts as a short with a very high ohms value via R1, R2, and R3
for a total of about 66 MegOhm so very high. When the phone line is cut (Tony van
Roon's open), it activates the MosFet (Tony van Roon's Q3) via transistor Q2 to drive
the load. Substitutes are fine, none of the components are critical..... [Tony
van Roon's circuit] |
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CW Zero Beat Indicator - The information below has now been supplemented by
Elwood WB0OEW who built and uses the unit. The pictures he refers to can be seen at
the bottom of this page…. |
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Data Multiplexer Adds Cursor to LED Display Driver - 03/30/95 EDN-Design
Ideas..... EDN is migrating links. This link is not verified. Search the "title"
EDN for new link. |
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DC Current Indicator #4 - The circuit below uses some common components to
turn on an LED whenever DC current above a certain level is detected. The
circuit uses a very popular LM393 dual voltage comparator from National Semiconductor
and a common 1N4148 signal diode. The diode acts as a crude 0.7v voltage
reference. Only one of the comparators inside the 8 pin package is used. A
pair of resistors across the diode forms a voltage divider, which produce a reference
voltage of about 0.015v..... [Designed by David A. Johnson] |
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DC Current Indicator 6 - The circuit below is a simple way to indicate when
DC current is flowing through a wire. The circuit is designed so it will turn on
a LED indicator light, whenever the voltage drop across a shunt resistor exceeds about
0.1 volts. The value of the resistor can be selected based on the desired
current flow. Although I show a circuit for 12v operation, the circuit can be used
over a wide range from 3v to perhaps 24v..... [Designed by David A. Johnson] |
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Digital Mains Voltage Indicator - ..... |
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Doorbell for the Deaf - This circuit provides a delayed visual indication
when a door bell switch is pressed. In addition, a DPDT switch can be moved from
within the house which will light a lamp in the door bell switch. The lamp can
illuminate the words "Please Wait" for anyone with walking difficulties..... by Andy
Collison] |
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Doorbell Indicator-Remote - This circuit should only be used with the
solenoid type chime doorbells, the electronic type that play tunes will not work here.
The hardest part for this circuit was the title. It is quite easy to miss the sound of
a doorbell if you are watching TV , this circuit gets round the problem by providing a
visual indication, i.e. a lamp..... by Andy Collison] |
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